I'll try to answer your questions the best I can.
First, you take care of a pond almost like a tank. I'll suppose this is a 75gal-125gal insert. You need good filtration and depending on the size of the pond would likely want to use a canister filter and 1-3 large sponge filters. I would also suggest using a media bag filled with good research grade carbon or pertatin, (Spelling) to keep things stable the first 4-6 weeks. If you start to get an algae bloom using an HOB with filter pad and an old sock over the top will flitler it out quickly. Pond snails work wonder in ponds and help keep things in check. If you have a crayfish or plan to give about 30-50 pond snails a 60 day headstart and they will clean the pond and feed the crayfish. I'd also get a small stiff bristle push broom to keep the bottom free of algae. Bottom algae gets slick and you will fall on your tushy everytime you step foot in the thing. Here again it is hard to say not knowing the pond size.
Next, comet gold fish may be able to survive the winter provided the pond is at least 4' deep and you can keep it from freezing over. I'd ask that in the goldfish section as the Golden Ones are different than reguar fish people. Natives will work as well with the same rules as above. Most crayfish can survive if given a place to burrow such as a large flower pot perched on a rock. The alturnative, if you want some really nice and pricey fish, is to purchase 175gal rubber livestock tank and put it in the basement or garage over winter. I know some floks use livestocktank floating heaters in winter. You can also use 2-3 submersable heaters with air running from the bottom next to them. Just never let the floating heater touch the sides, never ever! Here again it is hard to say without knowing the size.
As for wildlife, the smaller the fish the less worry. I raise livebearers and sometimes a cichlid or two outside in the summer and have never lost a fish to wildlife. I live on a wooded property and all around me each house has 3-10 wooded acers. You can purchase a small motion detecter light that will turn on and go off in just a few minutes. You can also get little motion activated alarms that turn on for a minute or two and rig them together. A few flower pots full of marigold flowers will also go a long way in keeping animals out of the pond. Almost forgot, don't place and rock or other structures connected to the sides that go out into the pond. No use providing a fishing pier for them.
If you have any other questions feel free to P.M. me.
